The present invention relates to the field of computer tomography, and more particularly, to tomographic backprojection and volume rendering using a multiple color channel, graphics rendering engine.
Volume visualization of real-time or recorded images encompasses not only viewing, but also construction of a volumetric data set from the more basic projection data obtained from a sensor source. Most volumes used in rendering are derived from such sensor data. A primary example being computer aided tomographic (CAT) x-ray data. This data is usually a series of two dimensional projections of a three dimensional volume. The process of converting this projection data back into a volume is called tomographic backprojection. The term tomographic backprojection or computer tomography (CT) is used to differentiate it from signal reconstruction; i.e., the rebuilding of a continuous function (signal) from a discrete sampling of that function. Once a slice or volume is tomographically reconstructed, it can be visualized using known rendering techniques.
Computer tomography (CT) provides an image representing a transfer slice (also referred to as a plane) of a body or an object. This slicing is accomplished by rotating an x-ray source into the detection means (e.g., a row (ID) or array (2D) of sensors) around the perimeter of the section of the body or object to be viewed. The source and detection means are typically placed 180xc2x0 from each other to allow the detection means to measure the attenuation of the beam as it passes through the plane (slice) of interest. When enough measurements have been taken, a computer system is utilized to mathematically interpret the data, which is then displayed as a slice or an entire volume (volume rendering) on a monitor (e.g., a computer screen) for diagnostic or control purposes.
The operations of tomographic backprojection and volume rendering have traditionally been commercially implemented by specialized, very expensive CT systems. Medical procedures that require this hardware are likewise expensive, in some cases limiting patient accessibility to such procedures. Therefore, a need exists in the art for an enhanced method, system and program product for performing these operations in a more efficient, less costly manner.
Tomographic backprojection using conventional graphics hardware has been performed in the art. For example, reference an article by Cabral et al. entitled xe2x80x9cAccelerated Volume Rendering and Tomographic Backprojection Using Texture Mapping Hardware,xe2x80x9d 1994 Symposium on Volume Visualization, pp. 91-98, ACM SIGGRAPH, October 1994, as well as U.S. Pat. No. 6,002,738. Presented herein are various enhancements to the general backprojection approaches described, for example, by Cabral et al.
The present invention provides, in one aspect, a method of image backprojection from a projection data set. This method includes: splitting the projection data set into a plurality of multi-channel textures, each multi-channel texture corresponding to a predetermined number of color channels of a multi-color rendering engine; simultaneously rendering the split projection data set using the color channels of the multi-color rendering engine to obtain intermediate results for each color channel; and accumulating the intermediate results of each color channel to generate separate rendered images, wherein multiple images are simultaneously rendered from the projection data set using the separate color channels of the multicolor rendering engine.
In another aspect, a diagnostic imaging method is provided which includes generating a projection data set, and reconstructing an image from the projection data set. The reconstructing includes: splitting the projection data set into a plurality of multi-channel textures, each multi-channel texture corresponding to a predetermined number of color channels of a multi-color rendering engine; simultaneously rendering the split projection data set using the color channels of the multi-color rendering engine to obtain intermediate results from each color channel; and accumulating the intermediate results of each color channel to generate separate rendered images, wherein multiple images are simultaneously rendered for the projection data set using the separate color channels of the multi-color rendering engine.
In still another aspect, a method of image backprojection from helical beam projection data is provided. Unless otherwise specified, helical beam projection data is used herein to refer to helical fan beam and/or helical cone beam projection data. The method includes: loading the projection data into multiple textures; for at least one texture, determining a texture distance change between pitch angles using at least some textures of the multiple textures; rendering the multiple textures using a graphics rendering engine, the rendering including adjusting a model space for rendering texture data associated with at least one projection angle for a constant texture distance using the determined texture distance change between pitch angles; and accumulating rendered images to produce a reconstructed image from the helical beam projection data.
In a further aspect, a diagnostic imaging method is provided which includes generating helical beam projection data and reconstructing an image from the helical beam projection data. The reconstructing includes: loading the projection data into multiple textures; for at least one texture, determining a texture distance between pitch angles using the at least some textures of the multiple textures; rendering the multiple textures using a graphics rendering engine, the rendering including adjusting a model space for rendering texture data associated with at least one projection angle for a constant texture distance using the determined texture distance change between pitch angles; and accumulating rendered images to produce a reconstructed image from the helical beam projection data.
Systems and computer program products corresponding to the above-summarized methods are also described and claimed herein. Further, other embodiments and aspects of the invention are also described in detailed and claimed.